The present exemplary embodiment relates to telescoping masts. It finds particular application in conjunction with pneumatically actuated telescoping masts, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
Pneumatically actuated telescoping masts are well known in the art, and are, for example, mounted on the roof of a motor vehicle such as an emergency vehicle or utility vehicle. Alternatively, mounting configurations may also involve the floor of a vehicle, allowing the telescoping mast to extend through the roof of the vehicle. The mast is generally used for positioning electrical devices, such as lighting fixtures, at an elevated point above the vehicle. The effect of a lighting fixture is to light a large area around the vehicle, thus allowing emergency procedures to be conducted under the light, such as at accident scenes or by utility work crews during power outages, for example. Pneumatically actuated telescoping masts are particularly advantageous for such uses, because they are lightweight, compact in the retracted position, and quickly transportable to a site by the vehicles on which they are mounted. Pneumatically actuated telescoping masts are extended and retracted using air under pressure and, in a fully extended use position, are usually vertical, although they can be inclined in the use position. The vehicle on which the telescoping mast is mounted typically includes a compressor and appropriate pneumatic controls for displacing the mast sections between retracted and extended positions.
In a typical mast, each telescoping section includes a hollow cylindrical body with a collar secured to an end thereof. The collar can include a keyway (or key) for rotationally interlocking the telescoping section with an adjacent telescoping section or sections. The collar can also provide reinforcement to the cylindrical body.
Many prior art masts utilize a collar at the top of each telescoping section that extends radially outwardly from the cylindrical body. Such collars are often bolted or otherwise secured to the cylindrical body of the telescoping section. This allows an adjacent (smaller diameter) cylindrical body of an adjacent connected telescoping section to be retracted into the larger diameter telescoping section. In this manner, each telescoping section can be retracted into the next larger telescoping section. It will be appreciated, however, that the collars limit the longitudinal extent to which a particular telescoping section can be retracted. That is, the radially-outwardly extending collar of the telescoping section being retracted will ultimately interfere with the collar of the telescoping section into which it is being retracted, thereby limiting further retraction. Accordingly, in a fully retracted state, such masts have a height that is generally determined by a length of the base telescoping section, and the combined height of each collar of each additional telescoping section of the mast.
For example, FIG. 1 shows a prior art pneumatically actuated telescoping mast assembly 10 having a base end mounted within a vehicle 12. More particularly in this respect, mast assembly 10 includes five telescoping mast sections 16, 18, 20, 22, and 24, of which mast section 24 is a base section mounted on floor 14 of vehicle 12. The other four mast sections 22, 20, 18, and 16 extend sequentially along mast axis A from base section 24, and satellite dish 26 is shown atop the uppermost mast section 16 together with a wiring box assembly 17 on which a light is mounted and which encloses the electrical wiring for satellite dish 26. In FIG. 1, mast assembly 10 is shown by solid lines in its fully extended position and, immediately above the vehicle roof, is shown by phantom lines in its fully retracted position. It will be appreciated that each of the telescoping sections includes a radially outwardly extending collar 64 that limits the extent to which each respective telescoping section can be retracted into an adjacent telescoping section.